The digging strategy that the tribes used was really screwed up. with such a large area you need to start on the periphery and throw the sand you are digging out of the circle.
You need to move the sand one time from an unsearched area and into an already searched area or out of the search are entirely.
As you search/clear an outer “ring” you then move in towards the center to a closer ring where you can throw the sand you are digging onto the already searched outer area without covering up areas you still have to search.
These contestants all seemed to be moving the sand around onto areas that they would need to search in the future.
You are right
Yeppers.